| 1. |
|
|
| 2. |
|
|
| 3. |
- Boesen, Jesper, 1971, et al.
(författare)
-
Developing mathematical competence: From the intended to the enacted curriculum
- 2013
-
Ingår i: Journal of Mathematical Behavior. - : Elsevier BV. - 0732-3123 .- 1873-8028. ; 33:1, s. 72-87
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the impact of a national reform in Sweden introducing mathematical competency goals. Data were gathered through interviews, classroom observations, and online surveys with nearly 200 teachers. Contrasting to most studies of this size, qualitative analyses were conducted. The results show that teachers are positive to the message, but the combination of using national curriculum documents and national tests to convey the reform message has not been sufficient for teachers to identify the meaning of the message. Thus, the teachers have not acquired the functional knowledge of the competence message required to modify their teaching in alignment with the reform. The results indicate that for complex reform messages, such as the competency message, to have intended impact on classroom practice, special attention needs to be put on the clarity of the message. To have high-stakes tests, for example, does not alone seem to be sufficient. © 2013 Elsevier Inc.
|
|
| 4. |
- Lithner, Johan, 1960-, et al.
(författare)
-
Mathematical competencies : A research framework
- 2010
-
Ingår i: Mathematics and mathematics education. - Linköping, Sweden : Svensk förening för matematikdidaktisk forskning, SMDF. - 9197393460 ; , s. 157-167
-
Konferensbidrag (refereegranskat)
|
|
| 5. |
- Apelqvist, G, et al.
(författare)
-
Dynamic and kinetic effects of chronic citalopram treatment in experimental hepatic encephalopathy
- 2000
-
Ingår i: Clinical neuropharmacology. - : Ovid Technologies (Wolters Kluwer Health). - 0362-5664 .- 1537-162X. ; 23:6, s. 304-317
-
Tidskriftsartikel (refereegranskat)abstract
- Chronic hepatic encephalopathy (HE) is a neuropsychiatric syndrome that arises in liver-impaired subjects. Patients with HE display various neuropsychiatric symptoms including affective disturbances and may therefore likely receive treatment with novel thymoleptics like citalopram (CIT). The simultaneous pharmacokinetic and pharmacodynamic outcome of the commonly used serotonin-selective thymoleptic drugs in liver-impaired subjects with pending chronic HE is far from understood today. We therefore investigated the effects of chronic, body-weight-adjusted (10 mg ╖ kg-1 ╖ day-1), treatment with CIT in rats with and without portacaval shunts (PCS). Open-field activity was monitored. The 5-HT, 5-HIAA, noradrenaline (NA), and dopamine (DA) output were assessed in the frontal neocortex. The racemic levels of CIT and its metabolites DCIT and DDCIT, including the S- and R-enantiomers, were determined in serum, brain parenchyma, and extracellular fluid. The rats with PCS showed higher (2-3-fold) levels of CIT than rats undergoing a sham treatment with CIT in all compartments investigated. The PCS rats also showed elevated levels of DCIT and DDCIT. No major differences in the S/R ratios between PCS rats and control rats could be detected. The CIT treatment resulted in neocortical output differences between PCS rats and control rats mainly within the 5-HT and DA systems but not within the NA system. For the 5-HT system, this change was further evidenced by outspoken elevation in 5-HT output after KCl-depolarizing challenges. Moreover, the CIT treatment to PCS rats was shown to "normalize" the metabolic turnover of 5-HT, measured as a profound lowering of a basal elevation in the 5-HIAA levels. The CIT treatment resulted in an increased or "normalized" behavioral activity in the PCS group. Therefore, a dose-equal chronic treatment with CIT in PCS rats produced pharmacokinetic and pharmacodynamic changes not observed in control rats. The results further support the contention of an altered 5-HT neurotransmission prevailing in the chronic HE condition. However, the tentatively beneficial behavioral response also seen following chronic CIT treatment to PCS rats in this study has to be viewed in relation to both the pharmacokinetic and pharmacodynamic changes observed.
|
|
| 6. |
- Axenrot, Thomas; Bergqvist, Björn; Carlstein, Mikael; Degerman, Erik,
(författare)
-
Fiskundersökningar i större vattendrag
- 2007
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- De större vattendragen (åar, älvar och floder) är ofta bristfälligtundersökta, trots att de ofta är kraftigt påverkade av mänskligaaktiviteter. Under senare år har behovet av undersökningari dessa vattendrag ökat eftersom EU:s ramdirektiv för vattenkräver övervakning av vattnens ekologiska status i alla typer avvatten. Det har också under senare förts fram önskemål om attkunna använda metoder som inte är destruktiva (dödande) vidkvantifi ering av fi skförekomsten i både sjöar och vattendrag.I syfte att utveckla icke dödande metoder för kvantitativafi skundersökningar i större vattendrag har under åren 2005och 2006 ett pilotprojekt omfattande både båtelfi ske ochhydroakustiska metoder (mobil horisontell ekolodning)genomförts i vattendragen Österdalälven (Älvdalens kommun)och Svartån (Örebro kommun). Projektet har genomförts som ettsamarbetsprojekt mellan Fiskeriverkets sötvattenslaboratorium,Systemekologiska institutionen vid Stockholms Universitet ochF.A.S.T. – Fiskeresursgruppen vid Älvdalens utbildningscentrum.Projektet har genomförts som ett utvecklingsprojekt inommiljöövervakningsprogrammet och har fi nansierats avNaturvårdsverkets Miljöövervakningsenhet.Arbetet har genomförts med målsättningen att metodiken skallvara tillämpbar för såväl övervakning av fi skresurserna somför miljöövervakning och bedömning av ekologisk status enligtramdirektivets krav. Dessutom skall metodiken kunna användasför uppföljning av de nationella miljökvalitetsmålen. Villkorsom måste uppfyllas är att metoderna skall ge informationom fi skbeståndens sammansättning, individtäthet ochstorleksfördelning utan att fi sken behöver dödas.I denna rapport redovisas resultatet av undersökningarna ochen jämförelse av de båda testade metoderna (båtelfi ske ochekolodning), dessutom ges rekommendationer för framtidaundersökningar i större vattendrag. Avsikten är att rapporten skallutgöra plattform för arbetet med att ta fram en standardiseradmetodik för undersökningar i större vattendrag som inte ärvadbara.
|
|
| 7. |
- Bengtsson, H, et al.
(författare)
-
Prevalence of abdominal aortic aneurysm in the offspring of patients dying from aneurysm rupture
- 1992
-
Ingår i: British Journal of Surgery. - : Oxford University Press (OUP). - 1365-2168 .- 0007-1323. ; 79:11, s. 1142-1143
-
Tidskriftsartikel (refereegranskat)abstract
- The prevalence of abdominal aortic aneurysm (AAA) is high in the brothers of patients with aneurysm. A genetic component in the development of AAA has, therefore, been postulated. In this study the offspring of patients who had died from AAA rupture were invited to undergo ultrasonography of the abdominal aorta. The attendance rate was 69 per cent. Thirty-nine sons of median age 60 (range 45-75) years and 23 daughters of median age 62 (range 42-80) years were examined. Abdominal aortic dilatation was found in eight men and one woman. The presence of aortic dilatation in these nine cases was not related to age, hypertension, smoking or symptoms of occlusive arterial disease. It is concluded that the sons of those who have died from ruptured AAA constitute a high-risk group for the development of this condition and should be considered for further screening.
|
|
| 8. |
|
|
| 9. |
- Bergqvist, Björn, 1965, et al.
(författare)
-
Effect of microwave radiation on permeability of liposomes. Evidence against non-thermal leakage
- 1994
-
Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 1872-8006 .- 0304-4165. ; 1201:1, s. 51-54
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of 2.45 GHz microwave radiation on the permeability of unilamellar phosphatidylcholine liposomes has been studied. Leakage of 5(6)-calboxyfluorescein from the liposomes was measured using spectrofluorimetry after exposure to either microwaves or thermal heating for 5-20 min intervals. The exposure temperature, 37.6 +/- 0.5 degrees C, was well above the phase transition temperature of the lipid membrane. The microwave exposure did not result in any non-thermal increase in permeability above that produced by thermal heating. This study refutes the results reported by Saalman et al. [1] in which an increased liposome permeability due to microwave exposure was reported. The refined analysis in the present study shows that this increased liposome permeability was not a non-thermal microwave effect.
|
|
| 10. |
- Bergqvist, David, et al.
(författare)
-
The economics of general thromboembolic prophylaxis
- 1988
-
Ingår i: World Journal of Surgery. - 1432-2323. ; 12:3, s. 349-355
-
Tidskriftsartikel (refereegranskat)abstract
- The clinical and economic effects of each of 3 alternatives—no prophylaxis, general prophylaxis, and selective treatment—have been assessed in conjunction with 3 types of surgery—general surgery, the subset surgery for cholelithiasis, and elective hip surgery. The costs of thromboembolic and hemorrhagic complications have been calculated from the figures for 28 patients hospitalized at the Department of Surgery, Malmö General Hospital, Malmö, Sweden. The anticipated number of thromboembolic complications—and thus even the number of fatal pulmonary embolisms—can be minimized in all 3 types of surgery by means of general prophylaxis. General prophylaxis with low-dose heparin is, however, accompanied by the greatest incidence of hemorrhagic complications. Health care costs are minimized with general prophylaxis in elective hip and general surgery, while no prophylaxis is the best alternative in surgery for cholelithiasis. From the patient's point of view, general prophylaxis minimizes the duration of thromboembolic disease in general surgery as well as in elective hip surgery. In surgery for cholelithiasis, however, no differences in health loss for the individual are shown between the 2 main alternatives, no prophylaxis and general prophylaxis. Selective treatment means treatment after diagnosis of thrombosis with some screening method. The alternative selective treatment was the least satisfactory of those 3 studied.
|
|
| 11. |
|
|
| 12. |
- Bergqvist, Ingela, et al.
(författare)
-
The basic helix-loop-helix transcription factor E2-2 is involved in T lymphocyte development
- 2000
-
Ingår i: European Journal of Immunology. - : Wiley-VCH Verlagsgesellschaft. - 0014-2980 .- 1521-4141. ; 30:10, s. 2857-2863
-
Tidskriftsartikel (refereegranskat)abstract
- E2A, HEB and E2-2 genes encode a group of basic helix-loop-helix (bHLH) transcription factors that are structurally and functionally similar. Deletion of the genes encoding either of these proteins leads to early lethality and a block in B lymphocyte development. Evidence for a function in T lymphocyte development has, however, only been reported for E2A and HEB. To further elucidate the role of E2-2 at developmental stages that have proven difficult to study due to the early lethality phenotype of mice defective in E2-2, we generated and analyzed mice conditionally mutated in the E2-2 gene. These mice are mosaic with respect to E2-2 expression, consisting of cells with either one functional and one null mutated E2-2 allele or two null mutated alleles. Using this experimental model, we find that cells with a homozygous null mutated E2-2 gene are under-represented in B lymphocyte as well as T lymphocyte cell lineages as compared to other hematopoietic or non-hematopoietic cell lineages. Our data suggests that E2-2 deficiency leads to a partial block in both B and T lymphocyte development. The block in T cell development appears to occur at an early stage in differentiation, since skewing in the mosaicism is observed already in CD4+8+ double-positive thymocytes.
|
|
| 13. |
- Bergqvist, Karin, et al.
(författare)
-
The role of chloramines in treatment of diabetic foot ulcers: an exploratory multicentre randomised controlled trial
- 2016
-
Ingår i: Clinical Diabetes and Endocrinology. - : Springer Science and Business Media LLC. - 2055-8260. ; 2:6
-
Tidskriftsartikel (refereegranskat)abstract
- Background Chronic foot ulcers in diabetes are serious, costly and frequently difficult to heal. Recent guidelines conclude that new dressings and treatments generally fail to show superiority compared with standard of care. Several mechanisms are probably responsible for impaired healing of chronic foot ulcers, including inflammation and infection. Chloramines have presumed antiseptic and antibacterial properties, and have shown to be a useful treatment in odontology. Methods In an explorative open randomised controlled multi-centre study, we compared chloramine-based treatment with current standard of care for 12 weeks and follow-up for 24 weeks. Seventeen patients in each group, mean age about 70, duration of diabetes > 20 years and foot ulcers about 1.5 years, completed the 12 weeks study. Results After 5 weeks, the difference between the groups in relative reduction in ulcer area was statistically significant (p=0.016). Absolute change in ulcer area was first statistically significant within the chloraminetreated group after 2 weeks (p=0.026), after 8 weeks in the control group (p=0.0023), with significant difference between groups after 5 weeks (p=0.024). The approximate relative decrease per week was 19.4% (95%CI 12.2, 26.0; p<0.0001) in the chloramine-treated group and 11.7% (95%CI 6.4, 16.7; p<0.0001; between-group difference p=0.083). After 9 weeks 7 patients had healed in the chloraminetreated group, but only one in the control group (p=0.039). There were no statistically significant differences in wound healing at 12 or 24 weeks, and no marked differences in signs of infection, pain, quality of life (EQ-5D), or incidence of adverse events. Conclusions Chloramine-based treatment seems to be efficacious, particularly in the early phase of the care of infected diabetic foot ulcers. It is safe and easy to use, and could prove to be a valuable addition in the treatment arsenal, providing non-surgical debridement. Future studies will evaluate its role in wound care.
|
|
| 14. |
- Björck, Martin, et al.
(författare)
-
Fatal bleeding following delivery : a manifestation of the vascular type of Ehlers-Danlos' syndrome
- 2007
-
Ingår i: Gynecologic and Obstetric Investigation. - : S. Karger AG. - 0378-7346 .- 1423-002X. ; 63:3, s. 173-175
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: The vascular form of Ehlers-Danlos' syndrome (type IV) is a potentially lethal genetic condition because of rupture of major arteries, often in the peri-partum period. Case Report: We report a 31-year-old primipara who died from a rupture of the right subclavian artery. The patient had several symptoms and signs typical of the disease. The rupture occurred during the expulsion-phase of delivery but was recognized only on day 9. Conclusion: Early recognition is crucial to avoid maternal mortality due to this genetic disorder. Once the condition is suspected, the clinical diagnosis is straightforward.
|
|
| 15. |
|
|
| 16. |
- Carlsson, Björn, 1975-
(författare)
-
From achiral to chiral analysis of citalopram
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within the field of depression the “monoamine hypothesis” has been the leading theory to explain the biological basis of depression. This theory proposes that the biological basis of depression is due to a deficiency in one or more of three key neurotransmitter systems, namely noradrenaline, dopamine and serotonin which are thought to mediate the therapeutic actions of virtually every known antidepressant agent.Citalopram is a selective serotonin-reuptake inhibitor (SSRI) used for the treatment of depression and anxiety disorders. Citalopram is a racemic compound, in other words composed of a 50:50 mixture of two enantiomers (S-(+)-citalopram and R-(-)-citalopram) and with one of the enantiomers (S-(+)-citalopram) accounting for the inhibitory effect. At the time of introduction of citalopram the physician needed a therapeutic drug monitoring service to identify patients with interactions, compliance problems and for handling questions concerning polymorphic enzymes and drug metabolism. An achiral analytical separation method based on solid-phase extraction followed by high-performance liquid chromatography (HPLC) was developed for routine therapeutic drug monitoring (TDM) of citalopram and its two main demethylated metabolites.As the data available on citalopram were from achiral concentration determinations and to be able to further investigate citalopram enantiomers effects and distribution, a chiral method for separation of the enantiomers of citalopram and its demethylated metabolites was established. The advances within chiral separation techniques have made measurement of the concentrations of the individual enantiomers in biological fluids possible.The process behind enantioselective separation is however not fully understood and the mechanism behind the separation can be further scrutinized by the use of multivariate methods. A study of the optimization and characterization of the separation of the enantiomers of citalopram, desmethylcitalopram and didesmethylcitalopram on an acetylated ß-cyclodextrin column, by use of two different chemometric programs - response surface modelling and sequential optimization was performed. Sequential optimization can be a quicker mean of optimizing a chromatographic separation; response surface modelling, in addition to enabling optimization of the chromatographic process, also serves as a tool for learning more about the separation mechanism.Studies of the antidepressant effect and pharmacokinetics of citalopram have been performed in adults, but the effects on children and adolescents have only been studied to a minor extent, despite the increasing use of citalopram in these age groups.A study was initiated to investigate adolescents treated for depression, with respect to the steady-state plasma concentrations of the enantiomers of citalopram and its demethylated metabolites. The ratios between the S- and R-enantiomers of citalopram and didesmethylcitalopram were in agreement with studies involving older patients. The concentrations of the S-(+)- and R-(-) enantiomers of citalopram and desmethylcitalopram were also in agreement with values from earlier studies. The results indicate that the use of oral contraceptives may have some influence on the metabolism of citalopram. This might be because of an interaction of the contraceptive hormones with the polymorphic CYP2C19 enzyme.Even though the SSRIs are considered less toxic compared with older monoamine-active drugs like the tricyclic/tetracyclic antidepressants, the risk of developing serious side effects such as ECG abnormalities and convulsions has been seen for citalopram, when larger doses have been ingested. Furthermore, fatal overdoses have been reported where citalopram alone was the cause of death. Data on the toxicity of each of the enantiomers in humans have not been reported and no data on blood levels of the enantiomers in cases of intoxication have been presented.An investigation was initiated on forensic autopsy cases where citalopram had been found at the routine screening and these cases were further analysed with enantioselective analysis to determine the blood concentrations of the enantiomers of citalopram and metabolites. Furthermore the genotyping regarding the polymorphic enzymes CYP2D6 and CYP2C19 were performed.In 53 autopsy cases, we found increasing S/R ratios with increasing concentrations of citalopram. We found also that high citalopram S/R ratio were associated with high parent drug to metabolite ratio and may be an indicator of recent intake. Only 3.8 % were found to be poor metabolizers regarding CYP2D6 and for CYP2C19 no poor metabolizer was found.Enantioselective analysis of citalopram and its metabolites can provide valuable information about the time that has elapsed between intake and death. Genotyping can be of help in specific cases but the possibility of pharmacokinetic interactions is apparently a far greater problem than genetic enzyme deficiency.
|
|
| 17. |
- Devi, Priya
(författare)
-
Molecular characterization of the hepatitis C virus core protein
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hepatitis C virus (HCV) is an RNA virus that causes chronic infection, which can lead to hepatocellular carcinomas in humans. Besides liver diseases, the chronic HCV infection causes a broad spectrum of extrahepatic complications such as lymphoproliferative, metabolic and autoimmune disorders. Notably, HCV encoded core (C) protein is the major virion component that is involved in the oncogenesis and immune subversion. Therefore, detailed molecular characterization of the C protein provides a rational starting point for identification of novel countermeasures against pathogenic HCV infections. In this thesis we have investigated the suppressive effect of the C protein on T cell functions in immortalized cell lines and clinical samples.In paper I, we found that the expression of the C protein enhanced overall tyrosine phosphorylation in immortalized T cells. Interestingly, stable expression of the C protein specifically reduced accumulation of the tyrosine phosphatase SHP-1 mRNA. Our detailed bisulfite sequencing (BS) studies revealed that the SHP-1 P2 promoter was particularly hypermethylated at CpG1 and proximal islands in these cells. In paper II, we presented a new high-throughput next generation bisulfite sequencing (NGS-BS) protocol for the analysis of locus specific CpG methylation in HCV-infected cells using SHP-1 P2 as a model promoter. In line with our data from the BS, the NGS-BS method showed similar methylation profile at CpG1 island in immortalized cells. Strikingly, peripheral blood mononuclear cells (PBMCs) isolated from healthy controls and HCV-positive (HCV+) patients, showed much lower levels of methylation at the CpG1 island with no significant difference in DNA methylation pattern. In paper III, we investigated the mechanism of the C protein-mediated release of Ca2+ from intracellular stores. We identified two distinct regions in the N- and C-terminal parts of the protein that were essential for activation of the Ca2+/NFAT pathway. Of these, the N-terminal region was required for self-association of the C protein into nucleocapsid-like structures whereas the C-terminal part is essential for anchoring the protein to the ER-membrane. In paper IV, we presented a PCR based diagnostic method for the specific detection of positive and negative strand HCV RNA using primers with a non-viral tag. The method was evaluated by analysing the plasma and PBMC samples from chronic HCV+ patients.Taken together, our studies provide more detailed molecular characterization of the HCV C protein functions in immortalized as well as in HCV+ T cells. Importantly, specific DNA methylation pattern of the SHP-1 gene promoter may function as a potential prognostic marker for the disease progression in HCV-induced tumors. In addition, our updated PCR-based HCV diagnostic method may provide a more specific tool to monitor HCV infections in minor reservoirs.
|
|
| 18. |
- Fredriksson, Sam, 1966, et al.
(författare)
-
Large eddy simulation of the tidal power plant Deep Green using the actuator line method
- 2017
-
Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 276:1
-
Konferensbidrag (refereegranskat)abstract
- Tidal energy has the potential to provide asubstantial part of the sustainable electric power generation. Thetidal power plant developed by Minesto, called Deep Green, is anovel technology using a ‘flying’ kite with an attached turbine,moving at a speed several times higher than the mean flow.Multiple Deep Green power plants will eventually form arrays,which requires knowledge of both flow interactions betweenindividual devices and how the array influences the surroundingenvironment. The present study uses large eddy simulations(LES) and an actuator line model (ALM) to analyze theoscillating turbulent boundary layer flow in tidal currentswithout and with a Deep Green power plant. We present themodeling technique and preliminary results so far.
|
|
| 19. |
- Fredriksson, Sam, 1966, et al.
(författare)
-
MODEL TIDAL POWER IN A TURBULENT OCEAN
- 2018
-
Ingår i: Oceanera-Net Final Conference, Edinburg, Scotland, 30-31 January 2018..
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 20. |
- Fredriksson, Sam T, et al.
(författare)
-
Tidal power plant simulations using large eddy simulation (LES) and the actuator line method (ALM)
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The share of the renewable energy in the gobal energy mix is to be increased according to the sustainable development goals of the UN. Tidal energy can here potentially play a substantial role for the electric power generation. The tidal power plant Deep Green developed by Minesto uses a novel technology with a “flying” kite that, with its attached turbine, sweeps the tidal stream with a velocity several times higher than he mean flow. Eventually these power plants will form arrays requiring knowledge of (1) the interaction between individual power plants as well as (2) how the power plants and the arrays will influence the surrounding environment. The tidally oscillating turbulent boundary layer flow is in the present study analyzed using Large Eddy Simulations (LES) utilizing two different modeling techniques (pseudo-spectral and finite volume method). The boundary layer flow is analyzed both undisturbed and with a sweeping tidal power plant. The power plant is modeled using the Actuator Line Method (ALM). This method has been reformulated in order to be able to take arbitrary pathways of the actuator line into account. The results for the undisturbed flow simulations show, e.g., variations of the turbulence intensity depending on pre- or post-tidal peak flow for equivalent volume mean flow. The results for the modeled power plant show, e.g., how the wake flow downstream of the power plant that can be related to the size of the pathway size.
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
- Fredriksson, Sam, 1966, et al.
(författare)
-
Turbulence Characteristics in Tidal Flows Using LES and ALM to Model the Tidal Power Plant Deep Green
- 2018
-
Ingår i: 4th AWTEC, Taipei, Taiwan, 2018.
-
Konferensbidrag (refereegranskat)abstract
- The turbulence in tidal flows affects the design and operation of tidal plants, e.g., through control system and dynamical loads. Present work is focused on a specific site west of Holy Island along the north west cost of Wales and a specific tidal power plant, Deep Green. Although, specific and applied, the work is generally applicable regarding findings and modelling techniques for other sites and designs. Large Eddy Simulations (LES) are used to study first the undisturbed tidal flow and then the flow with a power plant in operation. The undisturbed tidal flow simulations show that the turbulence characteristics differ between the acceleration and deceleration phase of the tidal cycle. The turbulence statistics are also used to estimate dynamical loads on the tidal plant with respect to, e.g., fatigue. Secondly, a novel Actuator Line Method (ALM) tidal power plant model, that e.g., takes the arbitrary trajectories of the power plant wing into account, is used. It’s used to study how the power plants affect the environment, available power downstream, and turbulence characteristics affecting other power plants in possible power plant arrays. It is shown that the width of the trajectory can be used as a measure to estimate the wake extent.
|
|
| 24. |
- Hansen, F, et al.
(författare)
-
Non-invasive measurement of pulsatile vessel diameter change and elastic properties in human arteries: a methodological study
- 1993
-
Ingår i: Clinical Physiology. - 1365-2281. ; 13:6, s. 631-643
-
Tidskriftsartikel (refereegranskat)abstract
- A recently developed ultrasound phase-locked echo-tracking system makes it possible to measure non-invasive pulsatile vessel diameter changes, and, in combination with blood-pressure measurement, to calculate pressure strain elastic modulus (Ep) and stiffness (beta). The reproducibility in measurements of pulsatile diameter changes with this system was evaluated. Also the precision of indirect blood-pressure measurements, as compared to the simultaneously measured intra-arterial blood pressure was tested. The resulting reproducibility in pressure strain elastic modulus (Ep) and stiffness (beta) was evaluated. Intra-observer variabilities in measuring pulsatile diameter changes were 16% for the abdominal aorta, 10% for the common carotid artery, and 15% for the common femoral artery, respectively. Intra-observer variabilities for Ep and beta were 21% for both in the abdominal aorta, 17% for both in the common carotid artery, and 18% for both in the common femoral artery, respectively. There were only small differences in indirect and direct measurement of systolic blood pressure, whereas indirect blood pressure measurement systematically overestimated the diastolic blood pressure, on average by 20%. The variabilities in indirect blood pressure measurements were 2% for the systolic and 3% for the diastolic blood pressure, respectively. Inter-observer variability in the investigation of the common carotid artery was 10% for the pulsatile diameter changes, and 21% and 23% for Ep and beta, respectively. Thus, the echo-tracking system represents a reliable system for estimation of pressure strain elastic modulus and stiffness. However, Ep and beta are systematically underestimated by 25-30%, when used in combination with indirect blood pressure measurements.
|
|
| 25. |
|
|
| 26. |
- Holmström, Erik, et al.
(författare)
-
On the sharpness of the interfaces in metallic multilayers
- 2004
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 101:14, s. 4742-4745
-
Tidskriftsartikel (refereegranskat)abstract
- We show that the three most relevant magnetic properties (magnetic moment, critical temperature, and interlayer exchange coupling) of metallic multilayers can be reproduced with good accuracy by first principles theory, provided that the picture of atomically sharp interfaces is abandoned and one allows instead for both interface alloying and interface roughness. The interface of a metallic multilayer (exemplified by the Fe/V system) is demonstrated to, at best, have interdiffusion essentially over two to three atomic layers on each side of the interface. Our conclusions are the result of combining experimental work with theoretical modeling, and we argue that this approach is the best avenue to obtain accurate information about the interface quality of metallic multilayers.
|
|
| 27. |
- Holmström, Erik, et al.
(författare)
-
Structural and magnetic aspects of multilayer interfaces
- 2004
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier. - 0304-8853 .- 1873-4766. ; 272-276, s. 941-
-
Tidskriftsartikel (refereegranskat)abstract
- We show that it is possible to obtain quantitative information about the interface quality by considering the magnetic moments of Fe/V multilayers. We derive a parameter space describing the quality of interfaces and argue that most of the experimentally grown samples lie within a smaller segment of this space.
|
|
| 28. |
- Kalaran, Hans, et al.
(författare)
-
Eigenmodes of a Loaded Reverberation Chamber
- 2022
-
Ingår i: IEEE International Symposium on Electromagnetic Compatibility. Volume 2022-September, 2022, Pages 212-215. - : Institute of Electrical and Electronics Engineers Inc.. - 9781665407878 ; , s. 212-215
-
Konferensbidrag (refereegranskat)abstract
- The analytical solution for a loaded reverberation chamber has been investigated. In consistence with earlier works, it is shown that adding a dielectric (non-absorbing) into the chamber will reduce the eigenfrequency of the chamber. This can be a step toward lowering usable frequency inside the Reverberation Chamber and representing the modes density similarly to an empty chamber.
|
|
| 29. |
- Karlsson, Kristian, et al.
(författare)
-
Electrical Fields in Vehicular Cavities During Reverberation Chamber EMC Immunity Test
- 2022
-
Ingår i: IEEE International Symposium on Electromagnetic Compatibility. Volume 2022-September, 2022, Pages 189-194. - : Institute of Electrical and Electronics Engineers Inc.. - 9781665407878 ; , s. 189-194
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we elaborate on EMC immunity tests in reverberation chambers of full-sized vehicles as well as these products' corresponding electromagnetic susceptibility. It is described how vehicles have regions or volumes (i.e., cavities), with sometimes installed hardware as well as software, which potentially is susceptible to electromagnetic interference, and how these cavities during test have properties (deterministic to ergodic) implying frequency-dependent properties of the electrical fields. Number of degrees of freedom for the electric fields is used to explain the behaviour of EMC, from deterministic coherent resonances and all the way to ergodic regions.
|
|
| 30. |
- Karlsson, Kristian, et al.
(författare)
-
Test Level in Reverberation Chamber EMC Immunity Assessment Based on the Quantile to Average Ratio
- 2022
-
Ingår i: IEEE International Symposium on Electromagnetic Compatibility. Volume 2022-September, 2022, Pages 178-182. - : Institute of Electrical and Electronics Engineers Inc.. - 9781665407878 ; , s. 178-182
-
Konferensbidrag (refereegranskat)abstract
- As more and more advanced electronics are incorporated into devices and vehicles, there is a need to improve and refine the test methods for performance assessment of electromagnetic compatibility. Traditional standards in reverberation chamber electromagnetic compatibility immunity assessment define the test level according to a calibration based on an average of maximum received electrical field probe readings. In this paper, we propose a converging approach based on the average, in combination with an additional offset to generate a quantile defined test level.
|
|
| 31. |
- Kern, Jhonnie, et al.
(författare)
-
Behovs- och systemanpassat underhåll av godsvagnar
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Dagens godstransportsystem på järnväg behöver åtgärdas för att förbättra såväl pålitlighet som punktlighet. Förevarande projekt syftar till att identifiera lösningar som enkelt kan implementeras och där effekter också enkelt kan beskrivas och förutses med avseende på underhåll och service av godsvagnar för morgondagens behov. Det bakomliggande syftet för dessa åtgärder är mer effektiva godstransporter. Tonvikt ligger i detta avseende på behovs- och systemanpassade åtgärder. Projektet syftar närmare till att utreda förutsättningarna för ett behovs- och systemanpassat underhåll av godsvagnar. Under projektets gång har mobila lösningar kring underhåll varit i fokus, varför rapporten riktar in sig på denna typ av underhåll. Trafikverket har bidragit med medel till projektet och utöver dem har Swemaint AB, BS Verkstäder AB och Handelshögskolan vid Göteborgs universitet medverkat i projektet. Föreliggande rapport redovisar resultaten av projektet.
|
|
| 32. |
- Kragsterman, Björn, 1961-
(författare)
-
Carotid Artery Stenosis : Surgical Aspects
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Randomised controlled trials (RCT) have demonstrated a net benefit of carotid endarterectomy (CEA) in stroke prevention for patients with severe carotid artery stenosis as compared to best medical treatment. Results in routine clinical practice must not be inferior to those in the RCTs. The carotid arteries are clamped during CEA which may impair the cerebral perfusion. The aim of this thesis was to assess population-based outcomes from CEA, investigate risk factors for perioperative complications/late mortality and to evaluate effects of carotid clamping during CEA. In the Swedish vascular registry 6182 CEAs were registered during 1994-2003. Data on all CEAs were retrieved, analysed and validated. In the validation process no death or disabling stroke was unreported. The perioperative stroke or death rate was 4.3% for those with symptomatic and 2.1% for asymptomatic stenosis (the latter decreasing over time). Risk factors for perioperative complications were age, indication, diabetes, cardiac disease and contralateral occlusion. Median survival time was 10.8 years for the symptomatic and 10.2 years for the asymptomatic group. Tolerance to carotid clamping during CEA under general anaesthesia was evaluated in 62 patients measuring cerebral oximetry, transit time volume flowmetry and stump pressure. High internal carotid artery flow before clamping and low stump pressure was associated with decreased oxygenation after clamping suggesting shunt indication. In 18 patients undergoing CEA, jugular bulb blood samples demonstrated significantly altered levels of marker for inflammatory activation (IL-6) and fibrinolytic activity (D-dimer and PAI-1) during carotid clamping as compared to radial artery levels. This indicates a cerebral ischaemia due to clamping although clinically well tolerated. In conclusion, the perioperative outcome after CEA in Sweden compared well with the RCTs results. Tolerance to carotid clamping may be evaluated by combining stump pressure and volume flow measurements. Although clinically tolerated clamping may induce a cerebral ischaemic response.
|
|
| 33. |
- Kragsterman, Björn, et al.
(författare)
-
Carotid Endarterectomy Induces the Release of Inflammatory Markers and the Activation of Coagulation as Measured in the Jugular Bulb
- 2017
-
Ingår i: Journal of Stroke & Cerebrovascular Diseases. - : Elsevier BV. - 1052-3057 .- 1532-8511. ; 26:10, s. 2320-2328
-
Tidskriftsartikel (refereegranskat)abstract
- Background and Purpose: Transient cerebral hypoxia may induce neuronal injury through an ischemia-reperfusion (I/R) response, with a subsequent activation of inflammation and coagulation-fibrinolysis. During carotid endarterectomy (CEA), the artery is clamped, which might impair the regional cerebral perfusion and initiate a local I/R response. Data suggest that the CD40-CD40 ligand dyad acts as a modulator in the induced activation. The aim of this study was to locally measure soluble CD40 ligand (sCD40L), in conjunction with inflammation and coagulation activation markers, during CEA.Subjects and Methods: This is a prospective study of 18 patients undergoing CEA. Blood samples from the venous jugular bulb (JB) and the radial artery (RA) were drawn at baseline and during the procedure. Measurements of sCD40L, interleukin-6 (IL-6), fragment 1 + 2 (F1 + 2), plasminogen activator inhibitor-1 (PAI-1), and D-dimer were analyzed. Comparisons during CEA were made between levels: baselines versus JB, JB versus RA, and sequential JB measurements. Fifty cardiovascular healthy patients were the reference group for the sCD40L baseline comparison.Results: Increased cerebral IL-6 levels were demonstrated throughout the procedure, as well as the temporal influence in F1 + 2, PAI-1, and D-dimer values. sCD40L remained unchanged throughout the procedure. This indicates a local cerebral inflammatory reaction together with an activation of coagulation-fibrinolysis, but it does not appear to primarily involve the CD40-CD40 ligand dyad.Conclusions: Signs of a local inflammatory reaction and activation of coagulation were observed during CEA, but levels of sCD40L remained stable, unaffected by carotid artery clamping and reperfusion.
|
|
| 34. |
|
|
| 35. |
|
|
| 36. |
- Kragsterman, Björn, et al.
(författare)
-
Long-term survival after carotid endarterectomy for asymptomatic stenosis
- 2006
-
Ingår i: Stroke. - 0039-2499 .- 1524-4628. ; 37:12, s. 2886-2891
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE - Large randomized trials have demonstrated a net benefit of carotid endarterectomy (CEA) for asymptomatic carotid artery stenosis compared with best medical treatment. However, it takes years to overcome the perioperative risk and gain the reduction in stroke or death risk. Long-term survival after CEA for asymptomatic stenosis may be an important consideration in deciding on this prophylactic procedure, but is not well documented. The aim was to analyze long-term survival after CEA for asymptomatic stenosis and the impact of risk factors in a population-based study. METHODS - The Swedish vascular registry (Swedvasc) covers all centers performing CEA. Data on all registered CEAs during 1994 to 2003 were retrieved. All patients were cross-matched with the Population-Registry for accurate data on mortality (date of death). Analyses with Kaplan-Meier curves for survival and relative odds ratio (OR) for predictors of survival were performed. RESULTS - A total of 6169 CEAs in 5808 patients were registered, with a median time at risk of 5.1 (range, 0.1 to 11.8) years. The indication for CEA was asymptomatic stenosis in 10.8% of the patients. Survival after CEA for asymptomatic stenosis was 78.2% after 5 and 45.5% after 10 years. Previous vascular surgery (OR, 1.8; 1.1 to 3.0), cardiac disease (OR, 1.7; 1.0 to 2.8), diabetes mellitus (OR, 2.3; 1.3 to 4.1), and age (OR, 1.5; 1.1 to 2.1 per 10 years) were predictors of decreased 5-year survival. CONCLUSIONS - In this population-based study of patients operated on for asymptomatic stenosis, a substantial reduction in long-term survival was observed. Predictors of decreased longevity were age at operation, diabetes, cardiac disease, and previous vascular surgery.
|
|
| 37. |
- Kragsterman, Björn, et al.
(författare)
-
Outcomes of carotid endarterectomy in Sweden are improving : resluts from a population based registry
- 2006
-
Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 44:1, s. 79-85
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: In large randomized trials, carotid endarterectomy (CEA) for asymptomatic stenosis has shown a net benefit compared with best medical treatment. To justify an increased number of procedures for this indication, the perioperative risk of stroke or death must not exceed that of the trials. The aim of this study was to evaluate the outcome in routine clinical practice in Sweden in a population-based study. METHODS: The Swedish Vascular Registry (Swedvasc) covers all centers performing CEA. Data on all registered CEAs during 1994 to 2003 were analyzed both for the whole time period and for two 5-year periods to study alterations over time. Four validation procedures of the registry were performed. Medical records were reviewed for both a random sample and a target sample (a total of 12% of the CEAs for asymptomatic stenosis). Swedvasc data were cross-matched with the In-Patient-Registry (used for reimbursement) and the Population-registry (death). RESULTS: A total of 6182 CEAs were registered, 671 being for asymptomatic stenosis. In the validation process, no missed registration of major stroke or death was found. Patients with asymptomatic stenosis had, when the whole time-period was analyzed, a perioperative combined stroke or death rate of 2.1%. Outcome improved over time; the combined stroke or death rate decreased from 3.3% (11/330) from 1994 to 1998 to 0.9% (3/341) from 1999 to 2003 (P = .026). During the second time period, no patient with a perioperative major stroke or death was reported. CONCLUSIONS: This extensively validated national audit of CEA for patients with asymptomatic carotid artery stenosis showed results well comparable with those of the randomized trials. The results improved over time.
|
|
| 38. |
- Kragsterman, Björn, et al.
(författare)
-
Risk factors for complications after carotid endarterectomy : a population-based study
- 2004
-
Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 28:1, s. 98-103
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The overall benefit of carotid endarterectomy (CEA) is dependent on the outcome from the procedure. However, many reports are from selected centres and not population-based. The aim of this study was to assess the 30-day complication rate for a whole country and also to determine independent risk factors for serious complications. MATERIALS AND METHODS: One thousand five hundred and eighteen CEA were retrospectively reviewed, covering principally all the CEAs in Sweden, during a three year period. Indications for surgery were; minor stroke 34%, TIA 34%, amaurosis fugax 18%, asymptomatic 11% and others 3%. Data were collected from the Swedish Vascular Registry (Swedvasc). Combined cohort and case-control methodology was used. RESULTS: Registered complications were; 43 permanent strokes, 32 transient strokes (<30 days), 18 TIA/amaurosis fugax and 22 deaths (seven fatal stokes). In the cohort study, the 30-day permanent stroke and death rate were 4.3% (65/1518). Significant risk factors in multivariate analyses were the indication for surgery (minor stroke vs. other indications) (p=0.02, RR=1.38), diabetes (p=0.02, RR=1.41), cardiac disease (p<0.01, RR 1.43) and operation at a university hospital (p=0.02, RR=1.39). In the case-control study comparing the 65 cases of permanent stroke and/or death with 130 matched controls the only significant risk factor was contralateral occlusion (p<0.01, OR=5.27). One patient (1/130) with a permanent stroke was wrongly reported as a local neurological complication (facial paresis). CONCLUSION: This national audit demonstrated population-based data on complication rates after CEA well comparable with previous randomised trials. The validity of the Swedvasc data was confirmed. Combined cohort and case-control methodology was useful in analysing risk factors for serious perioperative complications.
|
|
| 39. |
- Lundgren, Fredrik, et al.
(författare)
-
PTFE bypass to below-knee arteries : distal vein collar or not? A prospective randomised multicentre study
- 2010
-
Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 39:6, s. 747-754
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundPatency and limb salvage after synthetic bypass to the arteries below-knee are inferior to that which can be achieved with autologous vein. Use of a vein collar at the distal anastomosis has been suggested to improve patency and limb salvage, a problem that is analysed in this randomised clinical study.MethodsPatients with critical limb ischaemia undergoing polytetrafluoroethylene (PTFE) bypass to below-knee arteries were randomly either assigned a vein collar or not in two groups – bypass to the popliteal artery below-knee (femoro-popliteal below-knee (FemPopBK)) and more distal bypass (femoro-distal bypass (FemDist)). Follow-up was scheduled until amputation, death or at most 5 years, whichever event occurred first.ResultsIn the FemPopBK and in the FemDist groups, 115/202 and 72/150 were randomised to have a vein collar, respectively. Information was available for 345 of 352 randomised patients (98%).At 3 years, primary patency was 26% (95% confidence interval (CI) 18–38) with a vein collar and 43 (33–58) without a vein collar for femoro-popliteal bypass and 20 (11–38), and 17 (9–33) for femoro-distal bypass, respectively. The corresponding figures for limb salvage were 64 (54–75) and 61 (50–74) for femoro-popliteal bypass, and 59 (46–76) and 44 (32–61) for femoro-distal bypass with and without a vein collar, respectively. Log-rank-test for the whole Kaplan–Meier life table curve showed no statistically significant differences with or without vein collar primary patency: p = 0.0853, p = 0.228; secondary patency: p = 0.317, p = 0.280; limb salvage: p = 0.757, p = 0.187 for FemPopBK and FemDist, respectively. The use of a vein collar did not influence patency or limb salvage.ConclusionThis study failed to show any benefit for vein collar with PTFE bypass to a below-knee artery.
|
|
| 40. |
- Länne, T, et al.
(författare)
-
Diameter and compliance in the male human abdominal aorta: influence of age and aortic aneurysm
- 1992
-
Ingår i: European Journal of Vascular Surgery. - 0950-821X. ; 6:2, s. 178-184
-
Tidskriftsartikel (refereegranskat)abstract
- In this study changes in the diameter and compliance of the distal abdominal aorta (76 healthy Caucasian males, 5-71 years old) were determined non-invasively and related to age by means of an ultrasound phase-locked echo-tracking system. The diameter of the aorta increased not only in the period between 5 and 25 years of age, but also by about 30% between the ages of 25 and 71. The pressure diameter curves at 25, 51 and 70 years were non-linear with flattening between 90 and 110 mmHg, and the slope of the curves declined with age. Thus, the pressure strain elastic modulus (Ep) and stiffness (beta) increased (i.e. compliance decreased) in an exponential manner according to age. A group of 37 males with aneurysmal widening of the distal abdominal aorta had a significant increase in Ep when compared to an age-matched control group. Furthermore, the ranges for both Ep and beta were much larger in the aneurysm group than in the control group, indicating diversity in the pathogenesis of the disease. The non-invasive ultrasonic method of phase-locked echo-tracking is an appropriate method for studying compliance in major arteries under a variety of pathophysiological conditions.
|
|
| 41. |
- Länne, T, et al.
(författare)
-
Noninvasive measurement of diameter changes in the distal abdominal aorta in man
- 1992
-
Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 18:5, s. 451-457
-
Tidskriftsartikel (refereegranskat)abstract
- An ultrasound phase-locked, echo-tracking system was used to determine the dynamic properties of the distal abdominal aorta in 10 Caucasian male subjects (mean age, 25 years). Recordings were made at rest and during the blood pressure increase resulting from isometric exercise. The pressure diameter curve was nonlinear with an inflection at about 90-110 mmHg. Above this pressure range, the vessel was stiffer (less compliant), but the pressure diameter relationship was roughly linear above as well as below the inflection. Individual pressure diameter curves showed hysteresis, i.e., the aorta had a smaller diameter during expansion than during retraction at corresponding pressures. The pressure strain elastic modulus (Ep) and stiffness (beta) were at rest [Mean Arterial Pressure (MAP), 81 mmHg] 0.70 10(5) N/m2 and 6.0, respectively. During isometric exercise (MAP, 122 mmHg), Ep increased significantly by 91% and stiffness (beta) nonsignificantly by 27%. The variability of the compliance determinations was 5% when the ultrasonic system was combined with intra-arterial blood pressure measurements and less than 7% when combined with auscultatory blood pressure measurements. It is concluded that the phase-locked, echo-tracking system fulfills clinical requirements for routine measurements of vascular compliance.
|
|
| 42. |
- Martini, Helena, 1984, et al.
(författare)
-
Aerodynamic Effects of Roof Deflector and Cab Side Extenders for Truck-Trailer Combinations
- 2011
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
-
Konferensbidrag (refereegranskat)abstract
- Today there are a large variety of drag reducing devices for heavy trucks that are commonly used, for example roof deflectors, cab side extenders and chassis fairings. These devices are often proven to be efficient, reducing the total aerodynamic resistance for the vehicle. However, the drag reducing devices are usually identical for a specific pulling vehicle, independent of the layout of the vehicle combination. In this study, three vehicle combinations were analyzed. The total length of the vehicles varied between 10.10m and 25.25m. The combinations consisted of a rigid truck in combination with one or two cargo units. The size of the gap between the cargo units differed between the vehicle combinations. There were also three configurations of each vehicle combination with different combinations of roof deflector and cab side extenders, yielding a total number of nine configurations. The aim of this investigation was to determine the aerodynamic effects of the roof deflector and cab side extenders as a function of the type of vehicle combination. Important factors were the total length of the vehicle combination and the influence of the drag reducing devices further downstream. The investigation was performed using Computational Fluid Dynamics (CFD). The results from the investigation showed that the effect of the two drag reducing devices analyzed was different depending on the type of vehicle combination. It was established that the roof deflector and cab side extenders were always efficient in reducing drag both in 0° yaw and 5° yaw but the magnitudes differed between the configurations. The largest effects of the drag reducing devices were seen for the truck including the 1st cargo unit; the influence of the drag reducing devices on the 2nd cargo unit was smaller. The aerodynamic reductions were diminishing downstream, why it was concluded that it is of great importance to improve the aerodynamic design of the rest of the vehicle to maintain the positive effects of the drag reducing devices.
|
|
| 43. |
- Martini, Helena, 1984, et al.
(författare)
-
Aerodynamic Investigation of Gap Treatment- and Chassis Skirts Strategies for a Novel Long-Haul Vehicle Combination
- 2012
-
Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-3928 .- 1946-391X. ; 5:2, s. 616-627
-
Tidskriftsartikel (refereegranskat)abstract
- Constantly lowering emissions legislation and the fact that fuel prices have increased tremendously over recent years, have forced vehicle manufacturers to develop more and more energy-efficient vehicles. The aerodynamic drag is responsible for a substantial part of the total driving resistance for a vehicle, especially at higher velocities; thus it is important to reduce this factor as much as possible for vehicles commonly operating in these conditions. In an attempt to improve transport efficiency, longer vehicle combinations are becoming more common. By replacing some of the shorter vehicle combinations with longer combinations, the same amount of cargo can be transported with fewer vehicles; hence there is large potential for fuel savings. The knowledge of the aerodynamic properties of such vehicles is somewhat limited, and therefore interesting to study. This paper deals with the aerodynamic properties of a novel vehicle combination, which has a total length of almost 32m, and consists of a tractor unit in combination with two semi-trailers, supported by a dolly in-between the trailers. This vehicle combination was evaluated in terms of aerodynamic properties, by the use of numerical simulations in the form of Computational Fluid Dynamics [CFD]. Both the gap between the cargo-units and the irregular chassis of the trailers are known areas of substantial energy losses; it has also been shown in previous studies that a lot of the drag reduction that is created in the cab region is lost downstream. Hence it was of interest to investigate possibilities for improving these two areas. Two approaches to improve the flow in the gap region were evaluated: coverage of the gap and elimination of the gap. For the chassis treatment, chassis skirts were added along the entire vehicle combination. Eventually, these two strategies were added to investigate their combined effect. In addition, a more practical solution of the gap treatment was tested; a so-called gap-fairing system, which was applied to both semi-trailer units. The results from the simulations showed that there is great potential for the two drag-reducing strategies used. The combined gap treatment and chassis skirts were especially successful; the total drag coefficient was reduced significantly. It was seen that the chassis skirts were far more efficient compared to gap treatment; as a consequence of blocking the main part of the airflow at chassis level in yawed-wind conditions. The practical solution with a gap fairing was shown to be efficient, if used for both semi-trailer units.
|
|
| 44. |
- Martini, Helena, 1984, et al.
(författare)
-
Influence of Different Truck and Trailer Combinations on the Aerodynamic Drag
- 2011
-
Ingår i: SAE 2011 World Congress and Exhibition; Detroit, 12 April 2011. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
-
Konferensbidrag (refereegranskat)abstract
- The aim with this investigation was to study the aerodynamic properties of truck-trailer combinations of varying lengths. The aerodynamic properties of the combinations were evaluated in order to study similarities and differences in the flow field between different configurations. By the use of Computational Fluid Dynamics (CFD) six different types of truck-trailer combinations used for long hauling have been evaluated. The combinations have a total length varying between 10.10 m and 25.25 m and consist of either a tractor or rigid truck in combination with one or two cargo units. All of the combinations are commonly found on roads in Sweden and several other countries in Europe.The results from the simulations show that the aerodynamic propertiesdiffersignificantlyforthetruck-trailer combinations. It was found that the longer vehicle combinations are much more sensitive to yaw conditions than the shorter combinations. What was also evident is that the gap between the first and second cargo unit plays a significant role for the aerodynamic properties. Furthermore it was established that there is potential for fuel saving by a strategic choice of truck-trailer combination. According to the simplified evaluation made in this study the 25.25 m combinations show a lower power required per loading length (LL) and are therefore shown to be more efficient than the shorter combinations.
|
|
| 45. |
- Mellqvist, Johan, et al.
(författare)
-
Measurements of Industrial Fugitive Emissions by the FTIR Tracer Method (FTM)
- 1996
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A new method called the FTIR tracer Method (FTM) has been developed for mesuring and quantifying fugitive (diffuse) emissions of hydrocarbons. The method has been evaluated in field experiments whch were conducted in the vicinity of several petrochemical plants and an oil refinery during 1993-1995. The technique is based on concentration measurements with infrared remote sensing by Long Path Fourier Transform InfraRed (LPFTIR), combined with tracer releases. The field experiements show the FTM to be very useful for mass flux measurements of both alkanes and alkenes and that the measurements are consistent with the conventional SF6 method. However, the technique needs to be further validated and a more thorough understanding of the measurement uncertainties have to be achieved.
|
|
| 46. |
- Minelli, Guglielmo, 1988, et al.
(författare)
-
ACTIVE FLOW CONTROL FOR TRUCKS: FROM THEORY TO PRACTICE
- 2017
-
Ingår i: Svenska Mekanikdagarna, Uppsala, 12-13 juni 2017.
-
Konferensbidrag (refereegranskat)abstract
- The possibility to actively control the external aerodynamic of vehicles is an attractive yet challenging solution to decrease the aerodynamic drag and the fuel consumption. The workflow that describes the implementation of an Active Flow Control (AFC), for the suppression of theseparated flow at the A-pillar of a truck, is condensate in this paper. The presented work spans the process from a theoretical verification of the method to a preliminary implementation of an AFC on a real full-scale truck cabin. The study involves CFD and experimental work, including aerodynamic test in a full-scale wind tunnel. The milestones of this process are listed below:- Identification of the problem, Fig. 1.- Preliminary CFD (LES) study, Fig. 2.- CFD (PANS) study of a simplified truck cabin model, Fig. 3.- Experiments on a simplified cabin model and actuation of the flow, Fig. 4.- Full-scale preliminary test (cabin), Fig. 5.- Future: full-scale wind tunnel test (force measurements), cabin + trailer.- Future: piezo electric actuators.
|
|
| 47. |
- Nilsson, Mikael, et al.
(författare)
-
Measurement Uncertainty, Channel Simulation, and Disturbance Characterization of an Over-the-Air Multiprobe Setup for Cars at 5.9 GHz
- 2015
-
Ingår i: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers Inc.. - 0278-0046 .- 1557-9948. ; 62:12, s. 7859-7869
-
Tidskriftsartikel (refereegranskat)abstract
- Over-the-air (OTA) multiprobe setups provide an efficient way to characterize the performance of today's advanced wireless communication systems. In this paper, the measurement uncertainty of such a setup using a car as a test object is characterized through three experiments: measurement system analysis, channel sounder measurements, and probe coupling measurements. Four issues were in focus for the analysis: precision, realization of the wireless communication channel, coupling between the probes, and the influence of the test object size. The analysis shows that a large test object such as a car in an OTA multiprobe ring will affect the measurement uncertainty, but only to a small degree. The measurement uncertainty expressed as expanded uncertainty was below +/-1 dB, which is a level that would not violate best practice total uncertainty levels for comparable OTA methods.
|
|
| 48. |
- Nilsson, Mikael, et al.
(författare)
-
Multipath propagation simulator for V2X Communication Tests on Cars
- 2013
-
Ingår i: 2013 7th European Conference on Antennas and Propagation, EuCAP 2013. - 9788890701832 ; , s. 1342-1346, s. 1342-1346
-
Konferensbidrag (refereegranskat)abstract
- Test and evaluation of wireless communication performance with cars can be done in many ways. One approach, for both vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) tests, is to use a multipath propagation simulator to achieve realistic signal environments for the different communication systems under test. Multipath propagation simulators have previously been shown to be useful for testing mobile handsets. Specific issues related to tests with cars are the large size of the test object and the disturbances it can cause. In this paper we experimentally study how different design parameters of the multipath propagation simulator affect the received signals. The analysis of the setup as well as the data is performed using the so-called 'Design of Experiments' method.
|
|
| 49. |
- Nilsson, Mikael, et al.
(författare)
-
On Multilink Shadowing Effects in Measured V2V Channels on Highway
- 2015
-
Konferensbidrag (refereegranskat)abstract
- Shadowing from vehicles can degrade the performance of vehicle-to-vehicle (V2V) communication systems significantly. It is thus important to characterize and model the influence of common shadowing objects like cars properly. For multilink systems it is essential to model the joint effects on the different links. However, the multilink shadowing effects in V2V channels are not yet well understood. In this paper we present a measurement based analysis of multilink shadowing effects in V2V communication systems with cars as blocking objects. In particular we analyze and characterize the joint large scale fading process for multilink communication at 5.9 GHz between four cars in a highway scenario. From our analysis it is found that the coherence time of the large scale fading process for different links can vary from a few seconds to minutes. The results show that it is essential to consider the correlation of the large scale fading processes as the correlation coefficients can have both large negative and large positive values. There is also a clear indication that multihop techniques provide an efficient way to overcome the issue with shadowed cars in V2V systems.
|
|
| 50. |
- Skarpsvärd, Marcus, 1974-
(författare)
-
The Costs of Legal Certainty : A Forensically-Informed Methodology on How to Identify the Relevant Costs in Exclusionary Abuse Cases
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines the forensic relationship between unilateral price practices and prima facie exclusionary abuse(s) under Article 102 TFEU. The research aim is to ascertain relevant cost benchmarks that can be used to determine the legal qualification of a dominant firm’s price practices.The research syntheses and results reflect the law in force on the 1 February 2023 and are outcomes of applying the forensic method. The forensic method was applied by systematising the relevant financial data together with the legal sources for the purpose of categorising impugned price behaviours as exclusionary or competition on the merits.The research demonstrates, inter alia, that the legal use of cost benchmarks is entrenched in concept of the rule of law by seeking to strike a balance between legal certainty and the effectiveness of Article 102 TFEU. In order to realise this objective, the Court of Justice has constructed three distinct legal tests and depending on which test that is used, it will have a significant impact on which cost benchmark(s) that is to be regarded as relevant. The first is the AKZO test, which is a fixed cost test as it explicitly states which cost benchmarks that must be used. The second is the great bulk of cost test, which is a semi-fixed cost test as it is limited to the objectives that the chosen cost yardstick must realise. The third is the as efficient competitor test, which is an open-ended cost test as it is limited to its aim. However, despite clarifications from the Court of Justice, the law on exclusionary pricing remains complex, ambiguous, and sometimes contradictory. To that end, whilst the research concludes that variable cost is an inappropriate benchmark to apply in service sectors, the research also reveals that lex lata allows for the use of variable cost in a manner which is so extensive that the cost yardstick ultimately will apply in an overlapping way. The legal overlap that follows makes Article 102 TFEU wide-ranging to the extent that legal contradictions will occur. The research concludes that the incoherence is the result of using the wrong yardstick over which to classify the cost under scrutiny.Based on the research results, the dissertation makes two main propositions to rectify the incoherence. First, the relevant cost benchmark ought to be the managerial forward-looking calculated out-of-pocket cost. Second, the relevant yardstick over which costs should be classified ought to be the period in which the accused dominant undertaking’s price practice is in force.
|
|
